1. Field of the Invention
The present invention relates to a combustion apparatus, and more particularly relates to a combustion apparatus adapted for use with a hot-water supply system, a boiler or the like.
2. Related Art
The xe2x80x9cthick and thin fuel combustionxe2x80x9d method known in the art is designed to burn a fuel gas in its thin state. At least one main flame formed by burning a thin gas and at least one auxiliary flame formed by burning a thick gas will be jetted in juxtaposition to each other in this prior art system. In detail, such a thin gas for forming the main flame is composed a volume of the gas premixed with an amount of air whose volume is about 1.6 times as much as the theoretical air for said gas. A thick gas for forming the auxiliary flame contains a lesser amount of air.
In the thick and thin fuel combustion method, the fuel gas is burned with such an excess of air so that flame temperature is kept relatively lower to produce a less amount of nitrogen oxides. Thus, some types of current house-held water heater are constructed using such burners of the thick and thin fuel combustion system.
An example of thick and thin fuel combustion apparatuses having been widely used is disclosed in the Japanese Patent Laying-Open Gazette No. 10-47614.
In the combustion apparatus shown in the Gazette No. 10-47614, a first array of main burner ports for jetting and burning a gas mixture of a concentration is disposed along at least one second arrays of auxiliary burner ports for jetting and burning a gas mixture of a higher concentration. Main flames, which formed in the main burner ports, are stabilized with heat which they receive from auxiliary flames made by the auxiliary burner ports.
Generally, smaller burner ports will make more stable fire flames. There-fore, each prior art apparatus as shown in Gazette No. 1-47614 usually comprise a burner port assembly composed of a few metal plates corrugated and laid one on another to form between them an elongated opening. This opening is divided into a first array of small main burner ports arranged longitudinally of said assembly. However, nodes as idle portions not making any fire flame will inevitably intervene between main burner ports, so that some regions thereof disposed close to such nodes are spaced far from the auxiliary burner ports. As a result, the main flames being formed in main burner ports in such regions are not likely to be stabilized.
An object of the present invention is therefore to provide an improved combustion apparatus that will stabilize combustion of a fuel gas.
In order to achieve this object, the present invention has employed the following improvements.
From a first aspect of the present invention, it provides a combustion apparatus with a burner port assembly that comprises an elongated first array of main burner ports for jetting and burning a fuel gas mixture of a concentration to make main flames. The combustion apparatus comprises also at least one second arrays of auxiliary burner ports for jetting and burning a further fuel gas mixture of a different concentration to make auxiliary flames, wherein the second arrays of said auxiliary burner ports extend along the first array of said main burner ports. The burner port assembly is constructed using inner and outer wall segments together with outermost wall segments or bands, wherein the inner and outer segments are corrugated to define between them openings serving as the main burner ports. The one of said band faces the corresponding one of said outermost segments so as to define between them collateral burner ports. A still further gas mixture to be jetted from and burnt at the collateral burner ports may either be of the same concentration as that for the auxiliary burner ports or of a medium concentration between said respective concentrations for the main and auxiliary burner ports.
Fire flames from such collateral burner ports will be formed adjacent to the basal portions of main flames, thereby stabilizing same to diminish the so-called problem of xe2x80x98lifting phenomenonxe2x80x99 during operation of the apparatus of the invention.
Such a stabilized combustion will be free from the phenomenon of flame pulsating, and scarcely emitting any noise. Almost complete and thorough combustion will be afforded to any rate of fuel gas fed to this apparatus, thereby diminishing the degree of incomplete burning of said fuel gas. Production of monoxide and any other toxic gases will now be reduced to a minimum, advantageously from an ecological point of view. Efficiency of energy is also improved for the fuel gas fed to this apparatus, thus enabling an accurate control of its quantity and rate.
As summarized above, the burner port assembly comprises the corrugated inner and outer segments together with the outermost bands. A space defined between the one corrugated outer segment and the corresponding outermost band facing it is herein divided into some discrete cavities, due to corrugation of said segment. These discrete cavities serve as collateral, burner ports having each a relatively small opening. In operation of the apparatus, significantly smaller but steady flames generated by the collateral burner ports will contribute to stabilization of the main flames as mentioned above.
The outermost bands incorporated into the apparatus of the invention give an addition to overall heat capacity of main burner ports. Therefore, even if occasionally heated by adjacent fire flames, the main burner ports would not be superheated to such a degree as possibly causing their thermal de-formation. By virtue of this feature, a higher xe2x80x98turndown ratioxe2x80x99 (T.D.R.) can now be adopted in this combustion apparatus.
From another aspect, the present invention provides a combustion apparatus with a burner port assembly that comprises an elongated first array of main burner ports for jetting and burning a fuel gas mixture of a concentration to make main flames. The combustion apparatus comprises also at least one second arrays of auxiliary burner ports for jetting and burning a further fuel gas mixture of a different concentration to make auxiliary flames, wherein the second arrays of said auxiliary burner ports extend along the first array of said main burner ports. The burner port assembly is constructed using inner and outer wall segments together with outermost wall segments or bands, wherein the inner and outer segments are corrugated to define between them openings serving as the main burner ports. The one of said outer segments faces the corresponding one of said outermost bands so as to define between them collateral burner ports. The second arrays of auxiliary burner ports comprise each a plate portion that cooperates with the corresponding one of outermost bands in order to define between them intermediate burner ports. A still further gas mixture to be jetted from and burnt at the collateral burner ports may either be of the same concentration as that for the auxiliary burner ports or of a medium concentration between said respective concentrations for the main and auxiliary burner ports. A yet still further gas mixture jetted from the intermediate burner ports is of another medium concentration between said respective concentrations for the main and auxiliary burner ports.
In this mode of the invention, the intermediate burner ports are provided between the outermost band constituting the first array of main burner ports and the plate portion as one of members constituting the second arralys of auxiliary burner ports. Therefore, at least three groups of fire flames made of respective gas mixtures of different concentrations will be generated in and along a broad central zone of the first array where the main burner ports are located close to the auxiliary burner ports.
In this case, fire flames from such collateral burner ports and intermediate burner ports will be formed adjacent to the basal portions of main flames, in addition to the flames from the auxiliary burner ports. Consequently, the main flames will be stabilized much more to avoid the problem of xe2x80x98pulsating combustionxe2x80x99 during operation of the apparatus of the invention.
Such a stabilized combustion will be free from the phenomenon of flame oscillation, and scarcely emitting any noise. Almost complete and thorough combustion will be afforded to any rate of fuel gas fed to this apparatus, thereby diminishing the degree of incomplete burning of said fuel gas. Production of carbon monoxide and any other toxic gases will now be reduced to a minimum, advantageously from an ecological point of view.
Also in this case, the collateral burner ports are relatively small discrete cavities divided by the corrugated outer segment, so that during operation of the apparatus significantly smaller but steady flames generated by the collateral burner ports will continue to stabilize the main flames as mentioned above.
Also, the outermost bands are incorporated in this apparatus in addition to the inner and outer wall segments forming the first array of main burner ports. Thus, the overall heat capacity of main burner ports will be increased due to such an incorporation of those bands. Even if these main burner ports would occasionally and sharply be heated by adjacent fire flames due to any slowdown in fuel combustion rate, they will not be superheated to such a degree as possibly causing their thermal deformation. By virtue of this feature, a higher xe2x80x98turndown ratioxe2x80x99 (T.D.R.) can now be adopted in this combustion apparatus.
Communicating openings may preferably be formed in and through each wall defining a gas mixture passage leading to the array of auxiliary burner ports. These openings bring the collateral burner ports into fluid communi-cation with said auxiliary burner ports.
A part of the gas mixture flowing through the said passage towards the auxiliary burner ports will be directed into the collateral burner ports, through such communicating openings.
The collateral burner ports may be discrete holes arranged longitudinally of the array of said main burner ports.
Considerably small but steady flames generated at such discrete collateral burner ports will be more effective to stabilize the main flames.
Also preferably, these collateral burner ports may consist of burner port holes of different opened areas and arranged longitudinally of the array of said main burner ports.
According to experiments done by the present inventors, it is apparent that such a structure of the array of collateral burner ports is also useful in achieving the purpose discussed above, and will be much more effective if the larger collateral burner ports alternate with the smaller ones.
Also preferably, each outermost band may be of a smaller height to cover a part of retracted regions defined in each corrugated outer wall segment, with the other retracted regions being left exposed to the outside of said band. Further, communicating openings formed in the wall of a gas mixture passage leading to the auxiliary burner ports may be opened to face the said exposed retracted regions.
In this example of the present apparatus, the said exposed retracted regions formed outside the outer wall segment are regions in a direct fluid communication with the collateral burner ports. Therefore, a part of the gas mixture flowing through the passage towards the auxiliary burner ports will surely be delivered to said collateral burner ports, with fire flames jetted there-from reliably stabilizing the main flames.
In a preferable mode of the apparatus of the invention, it comprises an air intake for receiving ambient air or a thin mixture of a fuel gas, a fuel intake for receiving the air and a thick mixture of said fuel gas, and a thin gas passage that brings the air intake into a fluid communication with the main burner ports so as to supply them with the gas mixture. This apparatus further comprises a thick gas passage in a fluid communication with the auxiliary burner ports, and a blending station in communication with the fuel intake so as to homogeneously intermix the fuel gas with the ambient air. In this apparatus, a part of the thick gas mixture prepared at the blending station will be given in part to the thin gas passage, with the remainder being forwarded into the thick gas passage.
Ratio in fuel concentration of the thin gas mixture (for the main burner ports) to thick gas mixture (for the auxiliary burner ports) can now be kept stable more easily. The air intake in this apparatus may need only to suck the ambient air, with a fuel feed nozzle being disposed in connection with the fuel intake. Neither premixing of a fuel gas with air to prepare a mixture outside the apparatus, nor control of fuel concentration in such a mixture, will be necessary any longer, thereby simplifying a hot-water supplier or the like.
In a further embodiment, a flame stabilizer may be disposed in a space in which the auxiliary burner ports are disposed, in order to divide this space into a plurality of stabilizing burner ports.
Such a modification of the present apparatus will be advantageous in that the flame stabilizer does not impair rigidity of this apparatus, but enabling an easier division of each auxiliary burner port into any desired number of small chambers as the stabilizing burner ports. The apparatus modified in this manner will ensure a long-term stable operation, and such stabilizing burner ports determining the shape of flames jetted therefrom can be changed or adjusted in any desired fashion.
A zigzag pattern of such stabilizing burner ports may be employed to be separated from each other by said strip-shaped flame stabilizer. The auxiliary burner port divided in this way into the plurality of portions (i.e., the stabilizing burner ports) is advantageous in that respective cross-sectional areas thereof can easily be designed appropriately to obtain an optimum flow speed of minute tributaries flowing through those stabilizing burner ports. Such fine portions of the auxiliary flame will be much steadier in their shape to thereby further stabilize the main flames formed of the thin gas mixture jetted from the main burner ports.
The combustion apparatus may further comprise an igniter emitting electric sparks to inflame the gas mixture being jetted from the main burner ports and the like. In this connection, the main burner ports in burner port assembly may be composed of several plate-shaped wall segments that are united with each other at narrow tie portions intervening between them. Some or all of these tie portions protrude upwards from the main burner ports to function as a target or targets on which the electric sparks will impinge.
It will be understood that the gas mixture will be jetted up while flowing closely to and passing by such protruded tie portions in the array of main burner ports, so that easy and ready inflammation of the gas mixture is now ensured in this apparatus.
The combustion apparatus of the invention may be constructed such that each array of the auxiliary burner ports are disposed along the corresponding array of main burner ports so as to jet and burn the gas mixture of a different concentration from that of the other mixture for main burner ports. This array of main burner ports mainly composed of wall segments further comprises outermost bands, with each band facing the corresponding outer wall segment to define between them an array of the collateral burner ports.